/*
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/*
 *    PolyKernel.java
 *    Copyright (C) 1999 University of Waikato, Hamilton, New Zealand
 *
 */

package weka.classifiers.functions.supportVector;

import weka.core.Capabilities;
import weka.core.Instance;
import weka.core.Instances;
import weka.core.Option;
import weka.core.RevisionUtils;
import weka.core.Utils;
import weka.core.Capabilities.Capability;

import java.util.Enumeration;
import java.util.Vector;

/**
 * <!-- globalinfo-start --> The polynomial kernel : K(x, y) = &lt;x, y&gt;^p or
 * K(x, y) = (&lt;x, y&gt;+1)^p
 * <p/>
 * <!-- globalinfo-end -->
 * 
 * <!-- options-start --> Valid options are:
 * <p/>
 * 
 * <pre>
 * -D
 *  Enables debugging output (if available) to be printed.
 *  (default: off)
 * </pre>
 * 
 * <pre>
 * -no-checks
 *  Turns off all checks - use with caution!
 *  (default: checks on)
 * </pre>
 * 
 * <pre>
 * -C &lt;num&gt;
 *  The size of the cache (a prime number), 0 for full cache and 
 *  -1 to turn it off.
 *  (default: 250007)
 * </pre>
 * 
 * <pre>
 * -E &lt;num&gt;
 *  The Exponent to use.
 *  (default: 1.0)
 * </pre>
 * 
 * <pre>
 * -L
 *  Use lower-order terms.
 *  (default: no)
 * </pre>
 * 
 * <!-- options-end -->
 * 
 * @author Eibe Frank (eibe@cs.waikato.ac.nz)
 * @author Shane Legg (shane@intelligenesis.net) (sparse vector code)
 * @author Stuart Inglis (stuart@reeltwo.com) (sparse vector code)
 * @version $Revision: 5808 $
 */
public class PolyKernel extends CachedKernel {

	/** for serialization */
	static final long serialVersionUID = -321831645846363201L;

	/** Use lower-order terms? */
	protected boolean m_lowerOrder = false;

	/** The exponent for the polynomial kernel. */
	protected double m_exponent = 1.0;

	/**
	 * default constructor - does nothing.
	 */
	public PolyKernel() {
		super();
	}

	/**
	 * Creates a new <code>PolyKernel</code> instance.
	 * 
	 * @param data
	 *            the training dataset used.
	 * @param cacheSize
	 *            the size of the cache (a prime number)
	 * @param exponent
	 *            the exponent to use
	 * @param lowerOrder
	 *            whether to use lower-order terms
	 * @throws Exception
	 *             if something goes wrong
	 */
	public PolyKernel(Instances data, int cacheSize, double exponent,
			boolean lowerOrder) throws Exception {

		super();

		setCacheSize(cacheSize);
		setExponent(exponent);
		setUseLowerOrder(lowerOrder);

		buildKernel(data);
	}

	/**
	 * Returns a string describing the kernel
	 * 
	 * @return a description suitable for displaying in the
	 *         explorer/experimenter gui
	 */
	public String globalInfo() {
		return "The polynomial kernel : K(x, y) = <x, y>^p or K(x, y) = (<x, y>+1)^p";
	}

	/**
	 * Returns an enumeration describing the available options.
	 * 
	 * @return an enumeration of all the available options.
	 */
	public Enumeration listOptions() {
		Vector result;
		Enumeration en;

		result = new Vector();

		en = super.listOptions();
		while (en.hasMoreElements())
			result.addElement(en.nextElement());

		result.addElement(new Option("\tThe Exponent to use.\n"
				+ "\t(default: 1.0)", "E", 1, "-E <num>"));

		result.addElement(new Option("\tUse lower-order terms.\n"
				+ "\t(default: no)", "L", 0, "-L"));

		return result.elements();
	}

	/**
	 * Parses a given list of options.
	 * <p/>
	 * 
	 * <!-- options-start --> Valid options are:
	 * <p/>
	 * 
	 * <pre>
	 * -D
	 *  Enables debugging output (if available) to be printed.
	 *  (default: off)
	 * </pre>
	 * 
	 * <pre>
	 * -no-checks
	 *  Turns off all checks - use with caution!
	 *  (default: checks on)
	 * </pre>
	 * 
	 * <pre>
	 * -C &lt;num&gt;
	 *  The size of the cache (a prime number), 0 for full cache and 
	 *  -1 to turn it off.
	 *  (default: 250007)
	 * </pre>
	 * 
	 * <pre>
	 * -E &lt;num&gt;
	 *  The Exponent to use.
	 *  (default: 1.0)
	 * </pre>
	 * 
	 * <pre>
	 * -L
	 *  Use lower-order terms.
	 *  (default: no)
	 * </pre>
	 * 
	 * <!-- options-end -->
	 * 
	 * @param options
	 *            the list of options as an array of strings
	 * @throws Exception
	 *             if an option is not supported
	 */
	public void setOptions(String[] options) throws Exception {
		String tmpStr;

		tmpStr = Utils.getOption('E', options);
		if (tmpStr.length() != 0)
			setExponent(Double.parseDouble(tmpStr));
		else
			setExponent(1.0);

		setUseLowerOrder(Utils.getFlag('L', options));

		super.setOptions(options);
	}

	/**
	 * Gets the current settings of the Kernel.
	 * 
	 * @return an array of strings suitable for passing to setOptions
	 */
	public String[] getOptions() {
		int i;
		Vector result;
		String[] options;

		result = new Vector();
		options = super.getOptions();
		for (i = 0; i < options.length; i++)
			result.add(options[i]);

		result.add("-E");
		result.add("" + getExponent());

		if (getUseLowerOrder())
			result.add("-L");

		return (String[]) result.toArray(new String[result.size()]);
	}

	/**
	 * 
	 * @param id1
	 *            the index of instance 1
	 * @param id2
	 *            the index of instance 2
	 * @param inst1
	 *            the instance 1 object
	 * @return the dot product
	 * @throws Exception
	 *             if something goes wrong
	 */
	protected double evaluate(int id1, int id2, Instance inst1)
			throws Exception {

		double result;
		if (id1 == id2) {
			result = dotProd(inst1, inst1);
		} else {
			result = dotProd(inst1, m_data.instance(id2));
		}
		// Use lower order terms?
		if (m_lowerOrder) {
			result += 1.0;
		}
		if (m_exponent != 1.0) {
			result = Math.pow(result, m_exponent);
		}
		return result;
	}

	/**
	 * Returns the Capabilities of this kernel.
	 * 
	 * @return the capabilities of this object
	 * @see Capabilities
	 */
	public Capabilities getCapabilities() {
		Capabilities result = super.getCapabilities();
		result.disableAll();

		result.enable(Capability.NUMERIC_ATTRIBUTES);
		result.enableAllClasses();
		result.enable(Capability.MISSING_CLASS_VALUES);

		return result;
	}

	/**
	 * Sets the exponent value.
	 * 
	 * @param value
	 *            the exponent value
	 */
	public void setExponent(double value) {
		m_exponent = value;
	}

	/**
	 * Gets the exponent value.
	 * 
	 * @return the exponent value
	 */
	public double getExponent() {
		return m_exponent;
	}

	/**
	 * Returns the tip text for this property
	 * 
	 * @return tip text for this property suitable for displaying in the
	 *         explorer/experimenter gui
	 */
	public String exponentTipText() {
		return "The exponent value.";
	}

	/**
	 * Sets whether to use lower-order terms.
	 * 
	 * @param value
	 *            true if lower-order terms will be used
	 */
	public void setUseLowerOrder(boolean value) {
		m_lowerOrder = value;
	}

	/**
	 * Gets whether lower-order terms are used.
	 * 
	 * @return true if lower-order terms are used
	 */
	public boolean getUseLowerOrder() {
		return m_lowerOrder;
	}

	/**
	 * Returns the tip text for this property
	 * 
	 * @return tip text for this property suitable for displaying in the
	 *         explorer/experimenter gui
	 */
	public String useLowerOrderTipText() {
		return "Whether to use lower-order terms.";
	}

	/**
	 * returns a string representation for the Kernel
	 * 
	 * @return a string representaiton of the kernel
	 */
	public String toString() {
		String result;

		if (getExponent() == 1.0) {
			if (getUseLowerOrder())
				result = "Linear Kernel with lower order: K(x,y) = <x,y> + 1";
			else
				result = "Linear Kernel: K(x,y) = <x,y>";
		} else {
			if (getUseLowerOrder())
				result = "Poly Kernel with lower order: K(x,y) = (<x,y> + 1)^"
						+ getExponent();
			else
				result = "Poly Kernel: K(x,y) = <x,y>^" + getExponent();
		}

		return result;
	}

	/**
	 * Returns the revision string.
	 * 
	 * @return the revision
	 */
	public String getRevision() {
		return RevisionUtils.extract("$Revision: 5808 $");
	}
}
